Load Data into Dropdownlist using SQL -server (no sqldatasource)

void filDDPN()

{

    DropDownList1.Items.Clear();

    DataTable subjects = new DataTable();

    using (SqlConnection con = new SqlConnection(ConnectionString))

    {

        try

        {

            SqlDataAdapter adapter = new SqlDataAdapter("SELECT [Period] FROM [tbl500_Periods] order by id desc", con);

            adapter.Fill(subjects);

            DropDownList1.DataSource = subjects;

            DropDownList1.DataTextField = "Period";

            DropDownList1.DataValueField = "Period";

            DropDownList1.DataBind();

        }

        catch (Exception ex)

        {

            // Handle the error

        }

    }

}